A physical cell identifier (PCID) is an identification of a sector or cell at the physical layer. The Primary Sync Signal (PSS) or physical layer ID and the Secondary Sync Signal (SSS), which is a physical layer cell ID group number, determine the PCID. In some networks, the physical layer ID can have values between zero and two, while the cell ID group number can have values between 0 and 167. The PCID can be determined from the physical layer ID and the physical layer cell ID group number as three times the cell ID group number plus the physical layer ID number. Thus, the PCID can take values between 0 and 503.
Because the number of available PCIDs are limited (e.g., in existing systems PCIDs can only have values between 0 and 503), PCID reuse is required in a cellular network. PCIDs are typically assigned manually (e.g., by an operator) when a sector is brought into service. However, for a given sector, when two (or more) neighboring sectors use the same PCID, confusion can occur during user equipment (UE) handoff between sectors. PCID confusion can lead to failed handovers and dropped UEs. Because the numbers of sectors cellular networks utilize are increasing, the occurrence of PCID confusion is increasing.
While a UE can report each neighboring base station's cell global identity (CGI), which is a unique identifier, the UE requires significant UE processing to report CGI and CGI reporting increases network control traffic. As a result, it may be impracticable for a base station to request each UE to report neighboring base station CGI in order to detect a PCID confusion scenario. Relying on a randomly selected UE limits processing and network traffic requirements, but delays resolution of PCID confusion (leading to reduction in handover performance) and does not guarantee that a PCID confusion scenario will be identified because the randomly selected UE may not be able to report the CGI of all neighboring base stations that may contribute to the PCID confusion scenario.